Proppant recovery system

ABSTRACT

An improved method and apparatus for removing proppant from fluid used in an oil and gas well for reuse in future operations. The proppant is separated from the well fluid and transported to a materials collection tank. A crane then transports the materials collection tank onto a processing boat. On the processing boat, the proppant is vacuumed from the materials collection tank to a hopper. The proppant is then discharged from the hopper into a holding tank for treatment and reuse. In a first alternative embodiment, two hoppers are positioned above each other so that the proppant can be added to the upper hopper and then fed by gravity to the lower hopper. A valving arrangement maintains vacuum within the interior of at least one hopper at all times to provide a continuous vacuum operation. A conduit discharges from the lower hopper into the holding tank.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of 35 U.S.C. 111(b)provisional application Serial No. 60/336,246 filed Nov. 2, 2001, andentitled Proppant Recovery System.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention relates to the disposal of oil and gas wellproppant used during the drilling and production of an oil and gas well,wherein a fluid carries excess proppant to a removal area at the wellhead for separating proppant from the fluid. Even more particularly, thepresent invention relates to an improved proppant recovery system thatcollects the excess proppant to later be reused with new proppant.

[0005] 2. Description of the Related Art

[0006] Proppant, e.g., sand, is pumped into wellbore fractures toincrease the surface area of the fracture. The increased surface areaallows for increased production from the fracture. However, not all ofthe proppant pumped into the wellbore deposits into the fracture.Instead, some of the proppant remains in the wellbore. This excessproppant must be removed from the wellbore for production from thefracture.

[0007] A typical well is designed with up to 10 proppant-fracturedzones. The stimulation technique involves the pumping of as much as300,000 pounds of proppant into each zone. During this process up to70,000 pounds of excess proppant may remain in the wellbore, which iscleaned out using coiled tubing. The proppant material contains a resincoating to facilitate adhesion in the reservoir, which restrictsdisposal.

[0008] Previously, this excess proppant had to be collected offshore,placed in big bags, contained and shipped to shore for incineration.This practice was costly, wasteful, and environmentally suspect.Engineering studies revealed that the properties of the excess proppantmade it suitable to be re-cycled in future operations with minimalimpact on fracture performance. While re-using proppant has become anaccepted practice with no noticeable effect on well productivity,logistically it had some limitations. The material still had to becollected offshore and transported onshore where it was stored forseveral months before being reloaded into the stimulation vessel forreuse in the next fracture treatment. This represents storage problemsand environmental contamination problems associated with exposure ofthese materials. Furthermore, even with no unforeseen delays, this wasstill a time consuming, e.g., 24-hour, two-way trip.

[0009] What is desired is a way to recycle the excess proppant in amanner that saves cost. It is also advantageous for the recycle systemto be more simple logistically than previous recycle systems. Ideally,but not necessarily, the recovery system would operate entirely on-sitewithout having to transport the excess proppant off-site for processing.Despite the apparent advantages of such a recovery system, to date nosuch recovery system has been commercially introduced.

SUMMARY OF THE INVENTION

[0010] The present invention provides an improved method and system forremoving excess proppant from fluid used in an oil and gas well andrecovering the excess proppant for reuse in future operations. Thepreferred embodiment includes separating the excess proppant from thewell fluid at the well site. The excess proppant falls via gravity fromsolid separators (e.g. shale shakers) into a material trough with achute. At the material trough, cuttings fall through the trough chuteinto a materials collection tank that has an access opening. A cranethen transports the materials collection tank onto a processing boat. Onthe processing boat, a blower forms a vacuum within the materialscollection tank interior via a vacuum line. Along the vacuum line is ahopper for receiving the proppant from the materials collection tank.The excess proppant is then discharged from the hopper into a holdingtank for treatment and reuse. Liquids (fluid residue) and solids(proppant) are thus separated from the vacuum line at the hopper beforethe liquids and solids can enter the blower. In addition, a drop tank isalso located along the vacuum line between the hopper and the blower tocollect any remaining fluids or solids in the vacuum line before theyreach the blower.

[0011] In the preferred embodiment, three suction lines are usedincluding a first line that communicates between the materialscollection tank and the hopper, a second suction line that extendsbetween the hopper and the drop tank, and a third suction line thatcommunicates between the drop tank and the blower.

[0012] In a first alternative embodiment, two hoppers are positioned oneabove the other so that the proppant can be added to the first, upperhopper via the suction line and then fed by gravity to the second, lowerhopper. A valving arrangement maintains vacuum within the interior ofthe upper hopper at all times to provide a continuous vacuum operation.A conduit discharges from the lower hopper into a holding tank.

[0013] Thus, the present invention comprises a combination of featuresand advantages that enable it to overcome various problems of priordevices. The various characteristics described above, as well as otherfeatures, will be readily apparent to those skilled in the art uponreading the following detailed description of the preferred embodimentsof the invention, and by referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] For a more detailed description of the preferred embodiment ofthe present invention, reference will now be made to the accompanyingdrawings, wherein:

[0015]FIG. 1 is a perspective view of the proppant recovery systemconstructed in accordance with the preferred embodiment.

[0016]FIG. 2 is a schematic view of the proppant recovery system vacuumline equipment constructed in accordance with the preferred embodiment;

[0017]FIG. 3 is a partial elevational view of the proppant recoverysystem constructed in accordance with the preferred embodiment.

[0018]FIG. 4 is a partial elevational view of the proppant recoverysystem constructed in accordance with the preferred embodiment.

[0019]FIG. 5 is a partial elevational view of the proppant recoverysystem constructed in accordance with an alternative embodiment.

[0020]FIG. 6 is a partial elevational view of the proppant recoverysystem constructed in accordance with an alternative embodiment.

[0021]FIG. 7 is a partial elevational view of the proppant recoverysystem constructed in accordance with an alternative embodiment.

[0022]FIG. 8 is a partial elevational view of the proppant recoverysystem constructed in accordance with an alternative embodiment.

DETAILED DESCRIPTION OF THE PREFERRED AND ALTERNATIVE EMBODIMENTS

[0023] Referring initially to FIGS. 1-4, there is shown a recoverysystem 10 constructed in accordance with the preferred embodiment. Therecovery system 10 removes excess proppant 14 from fluid used in an oiland gas well and recovers the excess proppant 14 for reuse in futureoperations. It should be appreciated that the system 10 can be used withany type of proppant material. The recovery system 10 separates theexcess proppant 14 from the well fluid on a drilling platform “A”. Theexcess proppant 14 and any residual fluid falls via gravity from solidseparators 12 (e.g. shale shakers) into a material trough 15 with achute 16. At the material trough 15, the proppant 14 falls through thetrough chute 16 into a materials collection tank 18 that has an accessopening 20. Alternatively, the recovery system 10 includes a compressedair blower (not shown) to assist the proppant 14 and any residual fluidthrough the chute 16 when the proppant 14 and residual fluid need to bebroken up. U.S. Pat. No. 6,179,070 provides an example of a materialscollection tank that can be used with the present invention and ishereby incorporated herein by reference for all purposes. A crane (notshown) then transports the materials collection tank 18 onto aprocessing boat “B”. It should be appreciated by those skilled in theart that any suitable transportation means may be used to transport thematerials collection tank 18. On the processing boat “B”, a blower 22 isin fluid communication with the materials collection tank 18 via avacuum line 24 from the materials collection tank to a hopper 26, avacuum line 28 from the hopper 26 to a drop tank 30, and a vacuum line32 from the drop tank 30 to the blower 22. The blower 22 thus forms avacuum within the materials collection tank 18 interior to transport theproppant 14 through the vacuum line 24 for discharge into the hopper 26.

[0024] Valve 34 operates to open and close the discharge 40 of thehopper 26. Initially, the valve 34 is closed while the hopper 26 isfilled with the proppant 14. When the hopper 26 is full, the valve 34 isopened to discharge the proppant 14 from the hopper 26 into a holdingtank 42 for processing and reuse. The proppant 14 is thus separated fromthe vacuum line 24 at the hopper 26 before the proppant 14 can enter theblower 28. In addition, the drop tank 30 is also located along thevacuum line 28 between the hopper 26 and the blower 22 to collect anyremaining proppant 14 in the vacuum line 28 before they reach the blower22.

[0025] Thus, the recovery system 10 recycles the proppant 14 in a mannerthat saves cost by providing an efficient recycling system. The recoverysystem 10 is also capable of operating entirely on-site without havingto transport the excess proppant 14 off-site for processing.

[0026] Patents describing transportation systems for wellbore solidsinclude U.S. Pat. Nos. 5,402,857; 5,564,509; 5,839,521; 5,842,529;5,913,372; 5,971,084; 6,009,959; 6,179,070B1; 6,179,071B1; and6,213,227B1, all incorporated herein by reference for all purposes.

[0027] Referring now to FIGS. 5-8, there is shown a proppant recoverysystem 110 constructed in accordance with an alternative embodiment. Thealternative embodiment proppant recovery system 110 of FIGS. 5-8 issimilar in overall layout to the preferred embodiment recovery system10. The difference is that instead of a single hopper 26, the suctionline 24 from the materials collection tank (not shown) communicates withan upper hopper 126. Instead of being a single hopper, however, thehopper 126 is an upper hopper positioned above a lower hopper 127. Theupper hopper 126 is still subjected to the vacuum applied by the blower(not shown) through the vacuum line 128 from the upper hopper 126 to thedrop tank (not shown) and the vacuum line (not shown) from the drop tankto the blower. Thus, the proppant recovery system 110 represents adouble hopper 126, 127 arrangement that replaces the single hopper 26 ofrecovery system 10.

[0028] As shown in FIGS. 5 and 6, valves 134, 136 control the flow ofthe proppant 14 between the upper hopper 126 and the lower hopper 127.The valves 134, 136 also control the flow of the proppant from the lowerhopper 127 to discharge 140 and then to holding tank 142. A usercontrols the valves 134, 136 using a control panel 146 and pneumatic orhydraulic controllers (commercially available) to direct flow from theupper hopper 126 to the lower hopper 127, and then to the holding tank142. Valves 134, 136 can be pneumatic actuated flex-gate knife valves,for example, manufactured by Red Valve Company, Inc. of Pittsburgh, Pa.,USA.

[0029] The upper valve 134 is initially closed (FIG. 5) so that suctionlines 124, 128 begin filling the hopper 126. As the hopper 126 becomesalmost filled, the valve 134 opens while the lower valve 136 remainsclosed (FIG. 6). In FIG. 6, both of the hoppers 126, 127 are subjectedto a vacuum. However, the vacuum does not prevent the proppant 14collected in the upper hopper 126 from falling through the valve 134 andinto the lower hopper 127. This transfer of the proppant 14 from theupper hopper 126 to the lower hopper 127 is shown in FIG. 6. As theproppant 14 is discharged from the upper hopper 126 to the lower hopper127, the valve 136 remains closed as shown in FIG. 6. This closure ofthe valve 136 ensures that the vacuum is maintained on the interiors ofboth of the hoppers 126, 127. Otherwise, if the valve 136 were opened,the vacuum would be lost.

[0030] Once the proppant 14 has been transported from the upper hopper126 to the lower hopper 127, the valve 134 is closed so that the valve136 can be opened. When this occurs, the upper valve 134 is in itsclosed position to preserve the vacuum within the upper hopper 126. Oncethat vacuum is preserved within the upper hopper 126, the valve 136 canthen be opened (FIG. 8) so that the proppant 14 within the lower hopper127 can be discharged into the discharge 140 and then into the holdingtank 142. The proppant 14 can then be held in the holding tank 142 fortreatment and reuse. The valving arrangement maintains vacuum within theupper hopper 126 at all times to provide a continuous vacuum operation.

[0031] While preferred embodiments of this invention have been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the spirit or teaching of this invention. Theembodiments described herein are exemplary only and are not limiting.Many variations and modifications of the system and apparatus arepossible and are within the scope of the invention. Accordingly, thescope of protection is not limited to the embodiments described herein,but is only limited by the claims which follow, the scope of which shallinclude all equivalents of the subject matter of the claims.

What is claimed is:
 1. A method of recovering proppant from fluid usedin an oil and gas well bore comprising: separating the proppant from atleast substantially all of the well bore fluid; transporting theseparated proppant to a materials collection tank; transporting thematerials collection tank to a proppant recovery area; forming a vacuumwithin a hopper with a blower, the blower being in fluid communicationwith the hopper; suctioning the separated proppant with a suction line;transporting the separated proppant via the suction line to the hopper;and discharging the separated proppant from the hopper into a holdingtank.
 2. The method of claim 1 wherein the oil and gas well is anoff-shore oil and gas well at an off-shore well site.
 3. The method ofclaim 2 further comprising transporting the separated proppant to asecond hopper and filling and emptying the hoppers in an alternatingsequence.
 4. The method of claim 3 further comprising separating thehoppers from one another with a valving member.
 5. The method of claim 2further comprising removing the separated proppant from the suction lineat the hopper.
 6. The method of claim 3 further comprising removing theseparated proppant from the suction line at the hopper.
 7. The method ofclaim 3 wherein the two hoppers are positioned vertically one on top ofthe other such that the separated proppant can flow via gravity from onehopper to the other hopper.
 8. The method of claim 7 further comprisingoperatively associating at least one valve with the hoppers to maintaina vacuum within the hopper when the separated proppant flows via gravityfrom the hopper to the second hopper or from the second hopper to theholding tank such that the separated proppant may be continuouslytransported from the materials collection tank.
 9. The method of claim 2further comprising using a crane to transport the materials collectiontank to the proppant recovery area.
 10. The method of claim 3 furthercomprising using a crane to transport the materials collection tank tothe proppant recovery area.
 11. The method of claim 2 wherein theproppant recovery area comprises an off-shore vessel.
 12. The method ofclaim 3 wherein the proppant recovery area comprises an off-shorevessel.
 13. The method of claim 2 further comprising processing theseparated proppant off-shore for reuse in oil and gas well operations.14. The method of claim 3 further comprising processing the separatedproppant off-shore for reuse in oil and gas well operations.
 15. Aproppant recovery system for recovering proppant from fluid used in anoil and gas well bore comprising: a separator for separating theproppant from at least substantially all of the well bore fluid; amaterials collection tank for receiving the separated proppant; a devicefor transporting the materials collection tank to a proppant recoveryarea; a hopper for collecting the separated proppant; a conduit fortransporting the separated proppant from the materials collection tankto the hopper; a power source for forming a vacuum within the hopper;and a holding tank for receiving the separated proppant from the hopper.16. The system of claim 15 wherein the oil and gas well is an off-shoreoil and gas well at an off-shore well site.
 17. The system of claim 16further comprising a second hopper for collecting the separated proppantfrom the hopper.
 18. The system of claim 16 wherein the device fortransporting the materials collection tank comprises a crane.
 19. Thesystem of claim 17 wherein the device for transporting the materialscollection tank comprises a crane.
 20. The system of claim 16 whereinthe conduit for transporting the separated proppant from the materialscollection tank to the hopper comprises a suction line.
 21. The systemof claim 20 wherein the suction line comprises a flexible hose.
 22. Thesystem of claim 17 wherein the conduit for transporting the separatedproppant from the materials collection tank to the hopper comprises asuction line.
 23. The system of claim 22 wherein the suction linecomprises a flexible hose.
 24. The system of claim 17 wherein the hopperand the second hopper are separated by a valving member.
 25. The systemof claim 17 wherein the hopper and the second hopper each furthercomprise inlet openings that allow the separated proppant to be added tothe hoppers and outlets that enable the hoppers to be emptied.
 26. Thesystem of claim 17 wherein at least one control valve controls flow ofthe proppant into each of the hoppers and wherein the at least one valveenables a user to direct the proppant from the hopper to the secondhopper and from the second hopper to the holding tank.
 27. The system ofclaim 26 wherein the at least one valve maintains the vacuum in thehopper for continuous transportation of the separated proppant to thehopper while the separated proppant flows to the second hopper and whilethe separated proppant flows from the second hopper to the holding tank.28. The system of claim 17 wherein the hopper and the second hopper arepositioned vertically one on top of the other such that the separatedproppant can flow via gravity from the hopper to the second hopper. 29.The system of claim 16 wherein the power source is a powered blower. 30.The system of claim 17 wherein the power source is a powered blower. 31.The system of claim 16 wherein the hopper is positioned in between thepower source and the holding tank in a suction line such that the hopperdefines a separator.
 32. The system of claim 17 wherein the hoppers arepositioned in between the power source and the holding tank in a suctionline such that each of the hoppers defines a separator.
 33. The systemof claim 16 further comprising a drop tank in between the power sourceand the hopper in a suction line for collecting any separated proppantor other materials.
 34. The system of claim 17 further comprising a droptank in between the power source and the hoppers in a suction line forcollecting any separated proppant or other materials.
 35. The system ofclaim 16 wherein the proppant recovery area comprises an off-shorevessel.
 36. The system of claim 17 wherein the proppant recovery areacomprises an off-shore vessel.
 37. The system of claim 16 wherein theseparated proppant is processed off-shore for reuse in oil and gas welloperations.
 38. The system of claim 17 wherein the separated proppant isprocessed off-shore for reuse in oil and gas well operations.
 39. Amethod of recycling proppant from fluid used in an off-shore oil and gaswell bore comprising: separating the proppant from at leastsubstantially all of the well bore fluid; transporting the separatedproppant to an off-shore proppant recovery area; processing theseparated proppant at the off-shore recovery area for reuse in welloperations.
 40. The method of claim 39 wherein transporting theseparated proppant to the proppant recovery area further comprisestransporting the separated proppant to a materials collection tank andtransporting the materials collection tank to the proppant recoveryarea.
 41. The method of claim 40 further comprising transporting theseparated proppant from the materials collection tank to a hopper anddischarging the separated proppant from the hopper into a holding tank.42. The method of claim 41 wherein transporting the separated proppantfrom the materials collection tank to the hopper further comprisesforming a vacuum within the hopper with a blower, the blower being influid communication with the hopper and suctioning the separatedproppant from the materials collection tank with a suction line.
 43. Themethod of claim 42 further comprising transporting the separatedproppant to a second hopper and filling and emptying the hoppers in analternating sequence.
 44. The method of claim 43 further comprisingseparating the hoppers from one another with a valving member.
 45. Themethod of claim 42 further comprising removing the separated proppantfrom the suction line at the hopper.
 46. The method of claim 43 furthercomprising removing the separated proppant from the suction line at thehopper.
 47. The method of claim 43 wherein the two hoppers arepositioned vertically one on top of the other such that the separatedproppant can flow via gravity from one hopper to the other hopper. 48.The method of claim 47 further comprising operatively associating atleast one valve with the hoppers to maintain a vacuum within the hopperwhen the separated proppant flows via gravity from the hopper to thesecond hopper or from the second hopper to the holding tank such thatthe separated proppant may be continuously transported from thematerials collection tank.
 49. The method of claim 42 further comprisingusing a crane to transport the materials collection tank to the proppantrecovery area.
 50. The method of claim 43 further comprising using acrane to transport the materials collection tank to the proppantrecovery area.
 51. The method of claim 42 wherein the proppant recoveryarea comprises an off-shore vessel.
 52. The method of claim 43 whereinthe proppant recovery area comprises an off-shore vessel.
 53. A proppantrecycling system for recycling proppant from fluid used in an off-shoreoil and gas well bore comprising: a separator for separating theproppant from at least substantially all of the well bore fluid; adevice for transporting the separated proppant to an off-shore proppantrecovery area; wherein the separated proppant is processed at theproppant recovery area for reuse in well operations.
 54. The system ofclaim 53 wherein the device for transporting the separated proppant tothe proppant recovery area comprises a materials collection tank forreceiving the separated proppant and a means for transporting thematerials collection tank to the proppant recovery area.
 55. The systemof claim 54 further comprising means for transporting the separatedproppant from the materials collection tank to a holding tank at theoff-shore well site.
 56. The system of claim 55 wherein the device fortransporting the separated proppant from the materials collection tankto the holding tank comprises a hopper for collecting the separatedproppant, a suction line for transporting the separated proppant fromthe materials collection tank to the hopper, and a power source forforming a vacuum within the hopper.
 57. The system of claim 56 furthercomprising a second hopper for collecting the separated proppant fromthe hopper.
 58. The system of claim 56 wherein the device fortransporting the materials collection tank to the proppant recovery areacomprises a crane.
 59. The system of claim 57 wherein the device fortransporting the materials collection tank to the proppant recovery areacomprises a crane.
 60. The system of claim 56 wherein the suction linecomprises a flexible hose.
 61. The system of claim 57 wherein thesuction line comprises a flexible hose.
 62. The system of claim 57wherein the hopper and the second hopper are separated by a controlvalve.
 63. The system of claim 57 wherein the hopper and the secondhopper each further comprise inlet openings that allow the separatedproppant to be added to the hoppers and outlets that enable the hoppersto be emptied.
 64. The apparatus of claim 57 wherein at least onecontrol valve controls flow of the proppant into each of the hoppers andwherein the at least one valve enables a user to direct the proppantfrom the hopper to the second hopper and from the second hopper to theholding tank.
 65. The system of claim 64 wherein the at least one valvemaintains the vacuum in the hopper for continuous transportation of theseparated proppant to the hopper while the separated proppant flows tothe second hopper and while the separated proppant flows from the secondhopper to the holding tank.
 66. The system of claim 57 wherein thehopper and the second hopper are positioned vertically one on top of theother such that the separated proppant can flow via gravity from thehopper to the second hopper.
 67. The system of claim 56 wherein thepower source is a powered blower.
 68. The system of claim 57 wherein thepower source is a powered blower.
 69. The system of claim 56 wherein thehopper is positioned in fluid communication with and between the powersource and the holding tank such that the hopper defines a separator.70. The system of claim 57 wherein the hoppers are positioned in fluidcommunication with and between the power source and the holding tanksuch that each of the hoppers defines a separator.
 71. The system ofclaim 56 further comprising a drop tank in fluid communication with andbetween the power source and the hopper for collecting any separatedproppant or other materials.
 72. The system of claim 57 furthercomprising a drop tank in fluid communication with and between the powersource and the hoppers for collecting any separated proppant or othermaterials.
 73. The system of claim 56 wherein the proppant recovery areacomprises an off-shore vessel.
 74. The system of claim 57 wherein theproppant recovery area comprises an off-shore vessel.